2004 5.0 GLE started overheating this year (mid-summer) at high (2500-3000) rpm's. I have clear hoses on the engine with no bubbles, replaced the raw water pump and the circulating pump. The heads have been off and are clear, as are the intake and exhaust manifolds and risers. The "y" pipe on this model has no flappers and is clear. The power steering exchanger is clear. I pulled the lower unit, everything is clear and tight. The thermostat has been checked and opens properly. The prior raw water impeller has been changed every year and never lost any blades. The temperature sending unit has been changed. An alternate overheat sending unit has been installed with no change of results. Scanning the engine with a IR temperature gauge shows the block, risers, manifolds, hoses at "normal" temperatures except for the front "half" of the thermostat housing where the overheat sending unit is located. That is reading ~200 deg. It's at the boatyard now They ran it with muffs and said it had good water flow. They are as lost as I. I'm really hoping for some divine words of wisdom to solve this and get me back on the lake.